What is the function of the spliceosome?

• A. It synthesizes mRNA
• B. It translates proteins
• C. It removes introns and ligates exons to produce mature mRNA
• D. It degrades mRNA

Answer: (C)

The spliceosome carries out RNA splicing: it recognizes intron–exon boundaries, removes the noncoding introns, and joins the remaining exons to produce mature mRNA that can be exported to the cytoplasm for translation. This involves two chemical steps and the formation of a lariat intermediate, driven by small nuclear ribonucleoproteins (snRNPs) and associated proteins. Because of this, the final transcript contains only exons, and alternative splicing can generate multiple protein variants from a single gene. In contrast, transcription makes mRNA from DNA, translation converts that mRNA into protein on ribosomes, and mRNA degradation breaks down transcripts—so the spliceosome’s essential role is removing introns and ligating exons to produce mature mRNA.